Bartlett, 25, came through the county's age-group setup and academy, going on to make nine centuries for Somerset, eight of those coming in first-class cricket
Somerset batter George Bartlett is to join Northamptonshire at the end of the season.
Bartlett, 25, has represented the Taunton county on 94 occasions across formats but departs for Wantage Road, seeking opportunities across formats, having made just eight T20 appearances in Somerset's stacked batting lineup.
He came through the club's age-group setup and academy, going on to make nine centuries for Somerset, eight of those coming in first-class cricket.
"I think that the time is right for me to look at new opportunities and have a bit of a reset," said Bartlett. "This will allow me to do that and I'm looking forward to the new challenge which I can hopefully grab with both hands.
"Somerset has been a massive part of my life and I've made some great memories here. There are great people at the club. I've been here since I was about nine years old, and I've loved every minute."
Bartlett made a century for Somerset earlier this summer against Nottinghamshire (Harry Trump/Getty Images)
Somerset director of cricket Andy Hurry added: "He can be proud of the part he played in our history over recent years, and the contributions he has made in our success on the field. I know he moves onto the next chapter of his career with very fond memories of his time here.
"After speaking with George, a fresh challenge with the opportunity of stronger white-ball opportunities is something we both agree is important for his career ambitions and development."
Bartlett's arrival at Northamptonshire follows the signing of fast bowler George Scrimshaw, who is set to join from Derbyshire. Tom Taylor, the allrounder, was revealed last week by The Cricketer to be leaving for Worcestershire.